mm/migrate: move movable_ops page handling out of move_to_new_folio()

Let's move that handling directly into migrate_folio_move(), so we can
simplify move_to_new_folio().  While at it, fixup the documentation a bit.

Note that unmap_and_move_huge_page() does not care, because it only deals
with actual folios.  (we only support migration of individual movable_ops
pages)

Link: https://lkml.kernel.org/r/20250704102524.326966-12-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Harry Yoo <harry.yoo@oracle.com>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Brendan Jackman <jackmanb@google.com>
Cc: Byungchul Park <byungchul@sk.com>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Eugenio Pé rez <eperezma@redhat.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Gregory Price <gourry@gourry.net>
Cc: "Huang, Ying" <ying.huang@linux.alibaba.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Jerrin Shaji George <jerrin.shaji-george@broadcom.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Joshua Hahn <joshua.hahnjy@gmail.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Mathew Brost <matthew.brost@intel.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Naoya Horiguchi <nao.horiguchi@gmail.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Peter Xu <peterx@redhat.com>
Cc: Qi Zheng <zhengqi.arch@bytedance.com>
Cc: Rakie Kim <rakie.kim@sk.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Cc: xu xin <xu.xin16@zte.com.cn>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/migrate.c b/mm/migrate.c
index 8c4d5837db53ce2b3479923e622523d7536bcbfb..61e98ed46f134490d130f3fe2c208a054e170aa2 100644 (file)
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1026,11 +1026,12 @@ static int fallback_migrate_folio(struct address_space *mapping,
 }
 
 /*
- * Move a page to a newly allocated page
- * The page is locked and all ptes have been successfully removed.
+ * Move a src folio to a newly allocated dst folio.
  *
- * The new page will have replaced the old page if this function
- * is successful.
+ * The src and dst folios are locked and the src folios was unmapped from
+ * the page tables.
+ *
+ * On success, the src folio was replaced by the dst folio.
  *
  * Return value:
  *   < 0 - error code
@@ -1039,34 +1040,30 @@ static int fallback_migrate_folio(struct address_space *mapping,
 static int move_to_new_folio(struct folio *dst, struct folio *src,
                                enum migrate_mode mode)
 {
+       struct address_space *mapping = folio_mapping(src);
        int rc = -EAGAIN;
-       bool is_lru = !__folio_test_movable(src);
 
        VM_BUG_ON_FOLIO(!folio_test_locked(src), src);
        VM_BUG_ON_FOLIO(!folio_test_locked(dst), dst);
 
-       if (likely(is_lru)) {
-               struct address_space *mapping = folio_mapping(src);
-
-               if (!mapping)
-                       rc = migrate_folio(mapping, dst, src, mode);
-               else if (mapping_inaccessible(mapping))
-                       rc = -EOPNOTSUPP;
-               else if (mapping->a_ops->migrate_folio)
-                       /*
-                        * Most folios have a mapping and most filesystems
-                        * provide a migrate_folio callback. Anonymous folios
-                        * are part of swap space which also has its own
-                        * migrate_folio callback. This is the most common path
-                        * for page migration.
-                        */
-                       rc = mapping->a_ops->migrate_folio(mapping, dst, src,
-                                                               mode);
-               else
-                       rc = fallback_migrate_folio(mapping, dst, src, mode);
+       if (!mapping)
+               rc = migrate_folio(mapping, dst, src, mode);
+       else if (mapping_inaccessible(mapping))
+               rc = -EOPNOTSUPP;
+       else if (mapping->a_ops->migrate_folio)
+               /*
+                * Most folios have a mapping and most filesystems
+                * provide a migrate_folio callback. Anonymous folios
+                * are part of swap space which also has its own
+                * migrate_folio callback. This is the most common path
+                * for page migration.
+                */
+               rc = mapping->a_ops->migrate_folio(mapping, dst, src,
+                                                       mode);
+       else
+               rc = fallback_migrate_folio(mapping, dst, src, mode);
 
-               if (rc != MIGRATEPAGE_SUCCESS)
-                       goto out;
+       if (rc == MIGRATEPAGE_SUCCESS) {
                /*
                 * For pagecache folios, src->mapping must be cleared before src
                 * is freed. Anonymous folios must stay anonymous until freed.
@@ -1076,10 +1073,7 @@ static int move_to_new_folio(struct folio *dst, struct folio *src,
 
                if (likely(!folio_is_zone_device(dst)))
                        flush_dcache_folio(dst);
-       } else {
-               rc = migrate_movable_ops_page(&dst->page, &src->page, mode);
        }
-out:
        return rc;
 }
 
@@ -1330,20 +1324,23 @@ static int migrate_folio_move(free_folio_t put_new_folio, unsigned long private,
        int rc;
        int old_page_state = 0;
        struct anon_vma *anon_vma = NULL;
-       bool is_lru = !__folio_test_movable(src);
        struct list_head *prev;
 
        __migrate_folio_extract(dst, &old_page_state, &anon_vma);
        prev = dst->lru.prev;
        list_del(&dst->lru);
 
+       if (unlikely(__folio_test_movable(src))) {
+               rc = migrate_movable_ops_page(&dst->page, &src->page, mode);
+               if (rc)
+                       goto out;
+               goto out_unlock_both;
+       }
+
        rc = move_to_new_folio(dst, src, mode);
        if (rc)
                goto out;
 
-       if (unlikely(!is_lru))
-               goto out_unlock_both;
-
        /*
         * When successful, push dst to LRU immediately: so that if it
         * turns out to be an mlocked page, remove_migration_ptes() will